CVE-2019-18889 in Symfony
Summary
by MITRE
An issue was discovered in Symfony 3.4.0 through 3.4.34, 4.2.0 through 4.2.11, and 4.3.0 through 4.3.7. Serializing certain cache adapter interfaces could result in remote code injection. This is related to symfony/cache.
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Analysis
by VulDB Data Team • 08/30/2025
The vulnerability CVE-2019-18889 represents a critical remote code execution flaw within the Symfony framework's caching component. This issue affects multiple versions including the 3.4 series up to 3.4.34, 4.2 series up to 4.2.11, and 4.3 series up to 4.3.7, making it a widespread concern across the Symfony ecosystem. The vulnerability stems from improper handling of serialization within cache adapter interfaces, creating a pathway for malicious actors to execute arbitrary code on affected systems.
The technical root cause of this vulnerability lies in the way Symfony's cache component processes serialized data when certain cache adapters are used. When developers utilize specific cache adapter interfaces that support serialization, the framework fails to properly validate or sanitize the serialized data before processing it. This creates an exploitation vector where attackers can craft malicious serialized objects that, when deserialized by the vulnerable cache component, trigger unintended code execution. The flaw is classified as a deserialization vulnerability, which aligns with CWE-502, specifically targeting the dangerous practice of deserializing untrusted data without proper validation.
The operational impact of this vulnerability is severe and far-reaching for Symfony applications. Attackers can leverage this weakness to execute arbitrary code on target servers with the privileges of the web application process, potentially leading to complete system compromise. The vulnerability is particularly dangerous because it can be exploited remotely without requiring authentication, making it an attractive target for automated attacks. Once exploited, attackers can establish persistent access, exfiltrate sensitive data, or use the compromised system as a launchpad for further attacks within the network infrastructure. This vulnerability directly maps to ATT&CK technique T1059.001 for command and scripting interpreter and T1078.004 for valid accounts, as it allows for code execution and potential privilege escalation.
Organizations using affected Symfony versions should immediately implement mitigations to protect their systems. The primary recommended approach is to upgrade to patched versions of Symfony where the vulnerability has been addressed through proper input validation and sanitization of serialized data within cache components. Additionally, developers should review their application code to ensure that cache adapters are not being used with untrusted data sources, and consider implementing additional security layers such as input validation, proper access controls, and monitoring for suspicious serialization patterns. Security teams should also implement network-based intrusion detection systems to monitor for exploitation attempts and establish incident response procedures to quickly address any potential compromises. The vulnerability demonstrates the critical importance of secure deserialization practices and proper input validation in modern web applications, particularly within frameworks that handle complex data serialization operations.